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The characteristics of δ-ferrite formed in continuously cast 18-8 austenitic stainless steel slabs have been studied. Concentration variation of δ-ferrite in slabs has a strong relation to the secondary dendrite arm spacing changes across the thickness of the slabs. Dissolution of δ-ferrite under the reheating conditions is mainly governed by diffusion of Ni and Cr between r and δ phases. In non-equilibrium state such as commercial process conditions, dissolution rate of b-ferrite is increased with increasing reheating temperatures up to 1290℃.

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Conventionally cast equiaxed, directionally cast columnar and perpendicular to the solidified direction of columnar(transverse) Rene 80 specimens were creep rupture tested at 760° 657㎫, 871℃ 353㎫ and 982℃ 157㎫. Due to the difference of the arrays of grain boundaries among the specimens, different creep crack initiation and propagation mechanisms operated. The columnar specimens showed good creep rupture properties. To investigate effect of section size on the creep rupture properties of Rene 80, the equiaxed, columnar and transverse specimens having two different section sizes were creep rupture tested at the same conditions as the above. The transverse and columnar specimens have evident section size effects but the equiaxed specimens were different. This may be explained as follows : if the cracks initiated, the relative section size effect of the specimen will reduce. So the initiated cracks increase the applied stress under constant toad conditions. But due to the irregular arrays of grain boundaries and coarse grains, the section size effect was not clear in the equiaxed specimens.

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Effect of solution treatment temperature as well as tensile test temperature on the microstructure and superplasticity of high strength 7475 Al alloy was studied in order to optimize the grain refining process and superplastic forming conditions. Maximum grain refining was achieved by an application of high temperature solution treatment at 520℃ (higher than usual practice of 480℃) and also the maximum superplastic elongation was obtained at the grain size minimum. Maximum grain refining by a high temperature solution treatment is attributed to the dissolution of more solute atoms which are reprecipitated to optimal distribution for recrystallization at overaging stage. High temperature tensile test at 535℃ brought better results(elongation of about 1500% at an initial strain rate of 2.1×10^(-3)/s) than that of 516℃(usual practice). Effective accomodation for grain boundary sliding, assisted by high temperature diffusion, is considered responsible for the results.

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The integral enthalpies of mixing △H for Cu-In, Cu-Sb, In-Sb and Cu-In-Sb liquid alloys were determined calorimetrically. The observed dependence of pH on the concentration of the binary and the ternary alloys could be described with the associate model. By the calculation of △H of the ternary alloys with the help of the associate model the parameters are fixed using the △H values of the base-binary liquid alloys.

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Joining of cemented titanium carbide (or cermet) to 304 stainless steel using three types of low-Ag content brazing alloy was made by torch heating and in Ar-atmosphere furnace. Variation of interfacial structure and joining strength with brazing alloy and process was investigated. Joining strength was determined by fracture shear loading and high shear strength value up to 257 ㎫ were obtained for the joints brazed with BCZA-Si alloy. The strong bonding is attributable to the formation of plate-like Fe-Co-Ni alloy product at the cemented TiC/brazing alloy interface, which composed of 58.6 %Fe, 19.2%Co, 11.2%Ni, 3.4%Cu, 2.6%Ti, 1.6%Si and 1.3%Cr. That alloy product is formed by the solid-solution reaction between binder components(Co & Ni) in cemented TiC and components(Fe, Ni & Cr) deposited/desolved from stainless steel. For the use of BCZC-A10 alloy, Cr-carbide and high Cr-content Fe-Cr alloy product was continuously formed at the cemented TiC/brazing alloy interface. That Cr-carbide caused to deteriorate the joining strength of joints brazed with BCZC-A10 alloys.

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To obtain fundamental informations for fine tungsten carbide powders, the preparation of fine tungsten carbide by vapor phase reaction of WCl_6-CCl₄-H₂ system has been carried out in the temperature range of 800-1300℃. The effects of reaction conditions on particle size and morphology of tungsten carbide powders have been investigated by utilizing X-ray diffraction, SEM and TEM techniques. The content of WC increased remarkably with increasing the reaction temperature and the maximum content was about 97% at 1100℃ in the condition of the flow rate of Ar gas 200㎖/min, H₂ gas 100㎖/min and CCl₄ gas 40㎖/min. The particle size of the reation products obtained at 1100℃ was about 0.05㎛ and the shape of WC was spherical. The particle size decreased linearly with increasing reation temperature. Also the crystallite size increased gradually with increasing reaction temperature.

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An Al_(88)Y₂Ni_(10) amorphus alloy was found to exhibit a Large elongation reaching about 30% in the low temperature range of 450 to 475K. The temperature range agrees well with that where a lot of the primary fcc-Al particles with a ultrafine grain size precipitate homogeneously. It is therefore concluded that the appearance of the large elongation is due to a crystallization-induced plasticity phenomenon. The new phenomenon may be interpreted to occur through the sequent process of inhomogeneous deformation along shear plane, followed by preferential precipitation of Al particles on the shear plane resulting from the deformation-induced increase in temperature and then propagation of the deformation site to other site resulting from the precipitation-induced strengthening in the deformed area.

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